using System;

public class Program

{

    public static void Main()

    {

        var figure = Console.ReadLine();

        var area = 0.0;

        if (figure == "square")

        {

            var a = double.Parse(Console.ReadLine());

            area = a*a;         

        }

        else if (figure == "rectangle")

        {

            var a = double.Parse(Console.ReadLine());

            var b = double.Parse(Console.ReadLine());

            area = a*b;         

        }

        else if (figure == "circle")

        {

            var radius = double.Parse(Console.ReadLine());

            area = Math.PI*(radius*radius);

        }

        else if (figure == "triangle")

        {

            var a = double.Parse(Console.ReadLine());

            var h = double.Parse(Console.ReadLine());

            area = a*h/2;

        }

        Console.WriteLine(Math.Round(area,3));

    }

}